George Osborne, the shadow chancellor, floated the idea in response to the publication of figures from the Institute for Fiscal Studies showing that the Treasury will have to raise the equivalent of £1,250 a year from every family in the UK to plug the black hole in the government's finances.

But Downing Street said that three-year public sector pay deals played "an important role in providing stability" and that the government had no plans to adopt the Tory plan.

In research presented on the BBC's Today programme, the thinktank said that the budget deficit would be 2.7% higher than the Treasury predicted at the time of the pre-budget report in the autumn and that this would lead to the government having to find an extra £39bn a year by 2015-16 to make up the shortfall.

Alistair Darling, the chancellor, announced in the pre-budget report that taxes would have to go up in the long term to cover the government's losses.

But the IFS said that the situation was now worse than Darling predicted. It said that, if the government wanted to fund the £39bn shortfall without raising taxes any more, it would have to impose a five-year freeze on all government spending.

Alternatively, if it wanted to raise the money entirely through taxes, then families would face a tax increase worth £1,250 a year on average. That would be equivalent to £24 a week, or £3.50 a day.

The IFS figures were much higher than those in the government's pre-budget report, partly because they included an estimate of £130bn for bank losses that the government had not included in its calculations.

Osborne told the Today programme that he agreed with the figures and that, if the Tories were elected, he hoped that controlling public spending would take "the bulk of the strain".

He said he "had not ruled out" tax increases but would "work hard to avoid them", instead reducing the costs of government, reconsidering whether major spending programmes were needed, changing the culture in Whitehall and seeking IT procurement savings.

And he said public sector pay needed to "reflect the prevailing economic conditions", adding: "I think we need to look at these three-year pay deals that the government came up with because they may be very inflexible at a time when of course the economic conditions are changing very quickly.

"We have set an example by saying that the very high salaries you get in the public sector, it's difficult to justify them going forward and that anyone in a quango who is paying themselves more than the prime minister, it's going to be very difficult to justify that to the Treasury."

The Tories have already said that they want to stop people working in quangos earning more than the £194,250-a-year salary paid to the prime minister.

"It sends a very powerful signal throughout the public sector that the age of excess is over and we need an age of restraint and responsibility," Osborne added.

He also expressed hope the UK would move out of recession by the end of the year, but said that would still make it "one of the longest recessions we have endured".

Later the prime minister's spokesman told journalists that Gordon Brown thought it would be wrong to revise the three-year pay deal, which cover workers such as nurses, police officers and teachers.

"The government's view on multi-year pay deals is that they play an important role in providing stability," the spokesman said.

The spokesman pointed out that last year, when inflation was going up, there were calls to revise the pay deals up, not down. He also said that, as well as providing stability to the government, the long-term settlements also offered some security to the workers involved.

Asked about the IFS predictions, the spokesman said: "What you have got to bear in mind is that since last autumn there has been a very sharp reduction in global trade." He said the government would be publishing its own forecasts in the budget, but that the global recession would have an effect on the UK and that "that obviously has an impact on tax receipts".